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Residents of Wisconsin town began reporting unexplained sounds Sunday night

Shaking or vibrating sensations accompany the sounds

City officials say they don't know what's going on

Mysterious explosions. Unexplained shaking. Something's going on in Clintonville, Wisconsin, but nobody seems to know what it is.

The sounds -- variously described as rattling pipes, clanging metal, thunder or firecrackers -- have continued on and off since early Sunday night in just one part of the small town of 4,600, located about 180 miles northeast of Madison.

Accompanying the sounds are vibrations that have shaken homes and household objects in the northeast corner of town, city manager Lisa Kuss said.

The sounds were loud enough Monday morning that a CNN journalist could hear them during a cell phone conversation with Kuss.

The baffling phenomenon does not appear to have caused any significant damage or injuries, according to Kuss.

No, said one one tongue-in-cheek Twitter user. It's clearly mole men launching their attack on the surface dwellers.

While the Wisconsin sounds have yet to be explained, mysterious booming noises are not all that unusual. Recent media accounts include reports from North Carolina, Idaho, Tennessee and others.

U.S. Geological Survey scientist David Hill even published a paper in 2011 called, "What is That Mysterious Booming Sound?"

In it, he said such sounds are so commonplace in upstate New York, they earned the nickname "Seneca guns." They're also well enough known to be named by residents of Belgium, the countries around the Bay of Bengal, Italy and Japan, among other places, he wrote.

While the specific source of such sounds is rarely found, natural explanations abound, Hill said.

One possible explanation is gas explosively escaping from underground rock formations. Another is a rock burst, which can happen when mining or quarrying uncovers long-buried rock, suddenly relieving stress and resulting in "locally loud, explosive reports."

Others include meteorites, a phenomenon known as "booming sands" or even distant thunder, sounds that Hill wrote can be carried for significant distances under proper atmospheric conditions.